Why does my final render image have white particles all over the lighting area?
This is noise, which will happen in complex scenes without enough samples.
Aside from increasing the number of samples, here are some other things you can try:

Enable Multiple Importance Sample for the lamp in Properties &gt; Object Data &gt; Lamp:


Adjust the Clamp in Properties &gt; Render &gt; Sampling. Note that as of 2.70 indirect samples can be clamped separately from direct samples.

Increase the filter glossy option (also in Render &gt; Light Paths) if you have rough glossy materials.


There are also some tricks you might be able to do with your materials, but it's hard to say what without looking at your file.

Also see these related questions:

How to avoid noisy renders in Cycles?

What is the Reason Cycles Creates Incorrectly Colored/Firefly Artifact Pixels?

What is multiple importance sample option


And the wiki page on reducing noise.